Low molecular weight hydrocarbons such as methane, ethane, propane, n-butane, and isobutane are often found in natural gas streams, and may also be present in crude petroleum streams. Water is also very often present in these streams, as water is typically present in petroleum-bearing formations. Under conditions of elevated pressure and reduced temperature, including those often seen in petroleum-bearing formations and in the processes used to recover such materials, mixtures of water and many of the described hydrocarbons, sometimes referred to as lower hydrocarbons, or other hydrate forming compounds tend to form hydrocarbon hydrates. These hydrates are sometimes referred to as clathrates. These hydrates are generally crystalline in structure where water has formed a cage-like structure around a lower hydrocarbon or other hydrate forming compound molecule. For example, at a pressure of about 1 MPa, ethane can form gas hydrates with water at temperatures below 4 degrees Celsius. At a pressure of 3 MPa, it can form gas hydrates with water at temperatures below 14 degrees Celsius. Temperatures and pressures such as these are commonly encountered in the environments seen and equipment used where natural gas and crude petroleum are produced and transported, including but not limited to pipelines. The formed hydrates can then agglomerate and cause blockages in the pipelines. A notable example would be pipelines used on the seabed. Such crude petroleum pipelines exposed to conditions on the seabed and succumbing to gas hydrate formation precipitated the oil leak accident in the Gulf of Mexico.
The formation and agglomeration of gas hydrates are of particular concern in pipelines, as they may contribute to and even cause pipeline blockages during the production and transport of natural gas or crude petroleum streams. As gas hydrates form and inside a pipe or similar equipment, they can block or damage the pipeline and associated valves and other equipment, leading to costly repairs and down time. To prevent such plugging, physical means have been used, such as removal of free water, and maintaining elevated temperatures and/or reduced pressures, but these can be impractical to implement, and otherwise undesirable because of loss of efficiency and production. Chemical treatments have also been utilized, but also have their limitations. Thermodynamic hydrate inhibitors such as lower molecular weight alcohols and glycols are required in large amounts, and attempts to recover and recycle these inhibitors can lead to other issues, such as scale formation. Other groups of low dosage hydrate inhibitors are also known. One group of low dosage hydrate inhibitors are known as kinetic inhibitors. Kinetic inhibitors have a major limitation in relation to the conditions where sub-cooling is high. For example, when the temperature reaches more than about 12° F. lower than the bubble point temperature of the gas hydrate, the low dosage kinetic inhibitors may not be effective. Thus there is a continued need for additives that allow the prevention and/or inhibition of gas hydrate agglomeration, in order to minimize unscheduled shutdowns, maintenance and repair, and to provide safer operation of production and/or transport facilities that utilize natural gas or crude petroleum streams.